1. Field of the Disclosure (Technical Field)
The disclosure is concerned with aerial vehicles. More particularly, pertains to a class of flying toys and promotional aircraft which are able to hover like helicopters, using a plurality of propellers for lift and flight control with a body which is primarily spherical in shape and wing appendages.
2. Background
For more than two centuries, multi propeller aircraft have been experimented with, starting with the fabled toy of Launoy and Bienvenu of 1783. These devices were and are limited mostly to hover-type flight modes, flying at low speeds for limited endurances and distances.
A number of flying toys are shaped like space ships, rockets, and/or conventional full-scale aircraft. Some fiction writers have conceived flying objects which are currently well beyond the ability of technology to fully realize. Among them are aircraft which use flapping feathers for locomotion and flight control. Currently, there exists no subscale powerplant which is strong enough to move such individual flight feathers fast enough to lift an aerial vehicle for either locomotion or flight control. One of the major difficulties with using single or low numbers of feathers for flight is that root relieving effectively destroys the lift distribution over the feather root and body. A feather arrangement will necessarily consume orders of more power per unit lift with respect to a conventional aircraft.
Conventional aerial vehicles use a propeller guard to limit or prevent catastrophic propeller damage. Conventional propeller guards may be heavy and may induce even greater levels of cross-flow drag and pitchback instability. Additionally, conventional training cross-arms are added to the landing gear at the bottom of the aircraft, thereby allowing the customer to learn how to fly the aerial vehicle. While partially protecting the aerial vehicle from downward strikes, conventional training cross-arms the aerial vehicle can be easily flipped over, inducing propeller damage. Conventional training cross-arms may be exceedingly heavy and draggy as they lie directly in the propwash close to the ground, which compromises maneuverability. The great weight of cross-arms also leads to a net downward shift in center of gravity which exacerbates pendulum instabilities.